The present invention relates generally to hydraulic snubbers, and, more particularly, to an improved self-contained end-of-stroke hydraulic snubber that is intended to decelerate and cushion movement of an actuator rod at either end of its stroke.
Hydraulic actuators are frequently fitted with separate snubbing mechanisms to decelerate and reduce the impact of the piston hitting the end of the cylinder at either end of its stroke. With the advent with electro-mechanical screw actuators, separate hydraulic snubber assemblies are frequently added to decelerate and cushion both ends of the actuator rod movement.
Hydraulic actuators used in flight simulator motion systems have been using end-of-stroke cushions integrated into the hydraulic cylinder for many years. When electrical actuators began to be used in motion systems in the early 1990""s, there was a need to incorporate snubbers to perform this cushioning function. In a hydraulic actuator, it is straight-forward to incorporate snubbing. In an electro-mechanical actuator, however, snubbing requires a separate add-on device for that purpose. One approach has been to use separate snubber cylinders packaged either inside or outside of the actuator at each end.
Details as to such prior art snubbers are shown and described in U.S. Pat. Nos. 5,931,739, 5,720,368, 5,509,511, 5,387,083, 5,271,485, 3,766,798 and 3,200,664, the aggregate disclosures of which are hereby incorporated by reference.
With parenthetical reference to the corresponding parts, portions or surfaces of the disclosed embodiment, merely for purposes of illustration and not by way of limitation, the present invention broadly provides (e.g., in FIG. 1) an improved single self-contained bidirectional end-of-stroke hydraulic snubbing device (20) that is operative to decelerate and cushion movement of an actuator rod (22) at either end of its stroke. The improved snubber broadly includes: a housing (21), a rod (22) movable relative to the housing; a single fluid-filled variable-volume chamber (23) communicating with a fluid sump (66) through an orifice (65), and a lost-motion mechanism (25) for selectively and controllably causing a reduction of the volume of the chamber by motion of the member approaching either end of its stroke; whereby the mechanism will force fluid from the chamber through the orifice to decelerate and cushion movement of the rod relative to the housing proximate either end of its stroke.
The chamber may possibly be defined between a piston and a cylinder, as shown in FIG. 1. Alternatively, the chamber may be defined between a cylinder and two pistons, as shown in FIG. 2. The cylinder may be concentric with the rod. The fluid sump may include an accumulator (68), which may be pressurized if desired. The lost-motion mechanism may include a first abutment member (26) mounted on the member to engage one portion of the wall of the chamber, and a second abutment member (28) mounted on the member to engage another portion of the chamber wall.
Accordingly, the general object of this invention is to provide an improved end-of-stroke snubbing device.
Another object is to provide a single snubbing device which may be mounted on an electro-mechanical actuator, and which may selectively and controllably decelerate and cushion movement of the actuator rod proximate either end of its stroke.
These and other objects and advantages will become apparent from the foregoing and ongoing written specification, the drawings, and the appended claims.